


Sonic Underground Royal

by LittleWingedKuriboh



Category: Persona 5, Sonic the Hedgehog - All Media Types
Genre: Crossover, Gen, P5R Spoilers, Sonic Underground conclusion
Language: English
Status: In-Progress
Published: 2020-06-24
Updated: 2020-08-01
Packaged: 2021-03-03 21:40:33
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 2,688
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24902473
Author URL: https://archiveofourown.org/users/LittleWingedKuriboh/pseuds/LittleWingedKuriboh
Summary: I'm Sonic, Sonic the Hedgehog! You're probably familiar with ME, but as for the black-eyed jester me coming from the burst of flames out of my back? Hoo boy, is that a story! And it goes a little something like,They made a vow, but their mother was never found...All because of a man named Maruki...





	1. I Believe

**Summary for the Chapter:**

> Sonic has been on countless other adventures, but none quite like this. One day, he is visited by a strange girl who puts him on a path to fulfill a prophecy that time had forced him to abandon. And that was thanks to a force far greater than himself OR his regular arch-nemesis...

I was only 3 or 4 when Eggman took over, and my brother and sister, just a few days old. Our family outlawed with a price on our heads, we were visited by Igor, who revealed the infamous prophecy to my mother. "Someday, you will reunite with your children to become the Council of Four." But, as you all know, that didn't end up happening. But I'm getting ahead of myself. Let me take it back to the forcefield mission. If I don't break through, Egghead'll put 'em up around every factory. Gotta do it to it!

**It's not a game**

**I'm not a robot**

**A.I. challenging you**

**I'm not a phantom**

**I'm in your face and**

**I'm here to see it through**

**Right before your eyes**

**Watch us multiply**

**Come to claim our rights**

**It's time**

"Just... a little... faster..."

"You're almost there, Sonic!" Tails' voice reassured me over the communicator at my wrist. "Give it all you've got!"

**As our power grows**

**Tryin' to stop us shows**

**Might as well go tryin'**

**To stop time**

"No way I'm stoppin'! Just... a little... more... HYA!"

**So you know that we're out there**

**Swatting lies in the making**

**Can't move fast without breaking**

**Can't hold on or life won't change**

**And our voices ring out, yeah**

**Took the mask off to be free**

**Fought it out in the debris**

**Now we know that life will change**

"Yes!" I placed the bombs and was out before I knew it. In more ways than one, hehe...

But when I woke up, I wasn't back home with Bernadette. The room I was in looked like a baby's room, and everything was blue with this weird dim glow to it. It was a darker blue than my fur, so at least I could tell myself apart from everything. There was a pretty fancy-looking desk in the center, and the pink hedgehog seated there beckoned me to sit across from her. "Sonic the Hedgehog, welcome to the Velvet Room..."

"Where am I?..."

"This place exists between mind and matter, dream and reality. It is a place only those bound by a "contract" may enter. I am Amy Rose, and I have been assigned as your attendant."

"Whoa, okay, I'm dreamin' right?"

"Indeed. The "you" in reality is currently still unconscious from your mission, safe at home. You are only able to experience this as a dream. Still, this _is_ surprising. The state of this room reflects the state of your own heart. To think a nursery would appear as such. You must miss your family dearly, _Prince_ Sonic..."

My eyes shot open. "How do you know about the prophecy?!"

"The cards show me all sorts of things." Amy shuffled a deck of tarot cards and layed two of them out, one of which I recognized as the Fool. "For example, the Chariot represents lingering pain. In your case, it would be the reality that Dr. Maruki created for you." She waved her hand over the card, showing a small projection of a more energetic version of her clinging to my side. With another wave of her hand, there was a human girl named Elise, to whom this "Maruki" had given my mother's throne. She was also, supposedly, my lover in that world...

And finally, she showed me Maruki himself, being defeated by the people he created this reality for. "His intentions seemed good, but he was actually a very twisted man." Amy explained. "In repairing the parts of their lives that caused them grief, he took away the foundation of their identities. One in particular seemed in an awful hurry to die..." She pointed to the boy in the black mask.

"Who _are_ these people?"

"They are called the Phantom Thieves of Hearts. You have their leader to thank for rallying them against Maruki and restoring your reality." She drew another card. "Death."

"WHAT?!"

"Worry not, it actually represents change. The Council of Four never came to be in the previous realities. This is a sign that such a fate can be changed. Do you have the resolve to challenge the distortion of this world?"

"Of course! Why wouldn't I?" I thought for a moment before saying anything else. "You're gonna talk to the others, right?..."

"Unfortunately, I am not permitted to speak even with _you_ for long. In fact, it seems my time is up. Do you remember how to find them?"

"The song in my heart..." When I woke up, I bolted for my guitar, the emerald hanging from my neck glowing brightly.

** It's time to **

** Unveil the hype you've been waitin' for **

** It's time to **

** Put an end to the question of who will win **

** It's us **

** I used to have bad feelings **

** Premonitions of us falling short **

** Now I have no fear **

** Since we're here **

** To fight it together **

** I believe **

** We can fly up in the sky **

** One day we may just **

** Be able to touch down on a star **

** Off the road we have to go **

** The roadless path we shall proceed until the end of our roles **

** There's no turning back for us **

** 'Cuz we will never give up **

"What was that?!"

"They're out there..."

That was the same song I performed at the music festival that night. I know they would've recognized me either way, but I just had to be sure. And just like clockwork, we were all back together with S.W.A.T. Bots breakin' down the door and lockin' onto us.

"Who _are_ you guys?"

"We're your brothers!"

"We are?"

They don't remember me?! I mean, I can't really blame them, they were so young. But still...

I got them out safe and waited two hours for them at Station Square. To my surprise, Amy showed up, too. "It is time for you to explore the power of your medallions." Before Maruki messed everything up, they would turn into our instruments. They're still important to us, but that part's gone now. Probably for good reason, because in retrospect, the mission Amy gave us makes a lot more sense.

She handed us each a blueprint of our instruments. "You know someone skilled with machines, don't you? Have them build you these, and then go to see someone named Zero. They will guide you on your journey from there..." And just like that, she was gone. I took the blueprints from the others and quietly led them to Tails' workshop.

"I'm all alone, now..."

"Not a chance, sis!"

I am thou, thou art I

Thou hast acquired a new vow

It shall become the wings of rebellion

that breaketh thy chains of captivity

With the rebirth of the Chariot and the Lovers Personas,

I have obtained the winds of blessing that

shall lead to freedom and new power


	2. Hedgehogs United

**Summary for the Chapter:**

> Sonic's assigned attendant of the Velvet Room, Amy Rose, leaves the hedgehogs in the care of a jackal tribe with reality-warping magic. And Sonic's heart's desire for a family? Well, it might just mean the end of it...

It didn't take Tails too long to get our weapons situated. I noticed mine was a bit different than last time. Sonia and I both used guns before, but Amy turned my guitar into a sword. It's actually kinda funny, I remember always wanting to be a knight when I was little. Mom even made me a tiny little gauntlet and a toy sword and everything. She told me bedtime stories about "a brave knight she named me after." It was nice...

Anyways, we were off to Sky Sanctuary to train with Zero. "Your medallions- three of the seven Sol Emeralds- are a source of great power. But to use that power to its fullest, you must find harmony amongst yourselves." He pulled a glowing red gem from his pocket. "This is a Phantom Ruby. Our tribe creates them. They are used to reshape reality in cases such as this."

A younger jackal spoke up. "Like a dream so real, if you bump yourself in it, your sleeping self will bruise."

Zero chuckled. "This is my son, Niru." Niru walked into the room and stood by his father's side. "Would you like to-"

"I thought you'd never ask!" Niru took the Phantom Ruby from his father. "The first test... begins now!"

The three of us were trapped in a room with a non-Mobian lion. Y'know, like the ones _you're_ familiar with, and are VERY hostile?! We would have to work together to get out alive, but all I could think about was making sure I didn't lose them again... Long story short, we failed...

"Your heart was good, but you used poor judgement, Sonia. And Manic, your actions were correct." Zero turned to look me dead in the eye. "Had you all worked _together_ , your escape would have been simple."

"I got us killed..." My knees gave out, and there were already tears streaming down my face. "I'm sorry... I didn't want to lose you or Mom ever again... I'm sorry... I'm so sorry..."

"It was indeed _your_ impulsiveness, _your_ rash actions, _your_ inability to work as a team that will mean the _end_ of your family-"

"Dad, wait!" Niru cut him off. "Sonic, you may have been impatient and impulsive, but I could _see_ in your eyes your desire to protect them! _That_ is harmony... You two!" He turned to Sonia and Manic. "Strive to find this in your training, which we'll continue tomorrow morning. Or, perhaps before..."

So, we continued our training, in spite of Eggman's efforts to capture us. Our instruments only become weapons if we're in harmony, how Amy and Tails managed to program that is beyond me. Manic's drumset caused an earthquake, I got mad at him 'cuz it's no good if the thing's flyin', and everything broke down. So much for harmony... But Sonia seemed to notice something about the dragon that we overlooked. "It doesn't land, it just hovers. And when Manic shot that rock at it, did you see how it veered away? I think it's an air elemental. If it touches the earth, it'll be destroyed."

"Nice goin', sis! Where do you get this stuff?"

"We like to call it "school"."

"Oh, y'mean like in those places that'll have your head on a silver platter if you get outta line?" It's all under Eggman's control, what did you expect? At least, that was how _I_ understood it. With us being in hiding, Bernie taught us everything we know.

"Manic, do you think you can shoot a plate of earth up to hit the dragon?"

"I can try." But instead of using his drumset, his Sol Emerald lit up, and a full-on boulder shot up and hit the thing square in the chest.

With the dragon defeated, Zero pulled us out of the Ruby's domain. "Young Manic, you were upset because your siblings had such incredible powers while you did not, but see now that the power you've awakened is the strongest of all..."

And as it turned out, "Manic the Groundshaker" wouldn't be the only one awakening a new power... But we're not quite there yet.

"Many souls in Robotropolis have been lost..."

Zero used the Phantom Ruby to project the current state of the city. Among those captured was a familiar fox. "Tails?!"

"We gotta go back! We gotta!"

"Sonic, please, you must listen-"

"I don't CARE if or not _you_ think we're ready to leave, I'm _going_ to save my friend!"

"Sonic Hedgehog, you may be the most impatient, aggravating, annoying, impulsive-" It felt like my sister would ramble on forever. "But I have _also_ learned that you have the biggest heart in the world. If you truly believe this is the right thing to do, we're with you."

And without much else said, we were off. Manic got us into Eggman's base with something called the "Mouse Patrol."

"The Mouse Patrol is the first mission the Phantom Thieves assigns to new recruits. Stealin' food n' stuff from Egghead's Palace." I know, I know, I had to ask Amy about that: they're not the same ones who defeated Maruki. I didn't even know they had the "Palace" thing in common, either, 'til she showed me. "Let's show 'em how it's done, Cerberus." A blue ember flashed out of his eyes and turned into a little lion cub.

"That's just sad, teaching kids to steal."

"Hey, ya gotta get by somehow. Besides, no way I'm strong enough to try and go after the Treasure."

"Treasure? Tch, please! The only thing Eggman would consider "treasure" is our kingdom turned to metal."

"N-no, the Treasure is the source of a person's distorted desire. Once we find Ma, it'll push the security level up, cause the Treasure to manifest, and then we can steal it and end all of this!"

"Could we discuss this later?" I chimed in. "Let's not forget about Tails."

Crawling through the vents to the main room, we saw Eggman talking with a squirrel guy that didn't look like a robot, like everyone else we saw. Cerberus started purring. "It's trying to say that the distortion isn't as strong here." Manic explained. "Kinda smart, actually, puttin' the Safe Room here of all places. That or we just wandered out."

It sounded like this guy knows Sonia. "But sir, how would I know where she is?"

"Because she's YOUR fiancé!"

"But you can't hold me responsible for her actions!"

Sonia let out an annoyed sigh. "Good ol' Elias, always walking the fine line..."

" _Barf!_ What do you see in that guy?"

"Nothing. I was..." She shuddered. "betrothed..."

Eggman and Elias finished their argument and a message popped up on the computer. "Interrogation status: subject approaching data-open brain state. All information available in 23 minutes."

We followed Manic back through the vent to the interrogation room and got Tails unhooked. That's when I heard it. "We've located Chaos! Implanting the Ruby now!"

I remember Bernie telling me stories about Perfect Chaos, how it could flood entire cities with its appearance alone... I've been scared to death of water ever since... Eggman must be using one of the Rubies to simulate the Chaos Emeralds! But, he wouldn't release it on Robotropolis, would he?

The others were already gone when I heard its roar...


	3. Open Your Heart

**Summary for the Chapter:**

> Eggman has done the unthinkable, releasing a Phantom Ruby-powered Perfect Chaos in Robotropolis, of all places! Sonic feels powerless to stop the creature, but in truth, he is far from it.
> 
> "You are slave. Want emancipation?"

"What's the matter? Are you simply going to watch? Are you letting a little water get in your way?"

Listen here, pal! Perfect Chaos is a _lot_ of water- AGH!

"I thought you said you didn't want to lose them again! You would slay _gods_ for the justice you believe in, to fulfill a prophecy lost to time... Vow to me! I am thou, thou art I... Thou whom would accept blasphemy for desiring such a loving family, call upon my name, and release thy rage! Show the strength of thy will to ascertain all on thine own, lest thou be chained... TO DESPAIR ITSELF!"

And now, the moment you've all been waiting for... "Come forth, Mephistopheles!"

So, yeah, that's how it happened. Personas are the strength of heart. And now, with a clear grasp of my desire, I can save my family!

"This power of mine...is yours. Kill it however you wish. Run wild to your heart's content!"

** Thunder, rain and lightning **

** Danger, water rising  **

** Clamor, sirens wailing **

** It's such a bad sign **

** Shadows of dark creatures **

** Steel clouds floating in the air **

** People run for shelter **

** What's gonna happen to us? **

** All the steps we take **

** All the moves we make **

** All the pain at stake **

** I see the chaos for everyone **

** Who are we? What can we do? **

** You and I are the same in the way that **

** We have our own desires that we won't change **

** **There is no way I can lose!** **

_**Can't hold on much longer** _

** But I will never let go! **

_**I know it's a one-way track** _

** Tell me now how long this'll last **

_**I'm not gonna think this way** _

** Nor will I count on others **

_**Close my eyes and feel it burn** _

** Now I see what I've gotta do! **

** Open your heart, it's gonna be alright! **

All's well that ends well, right? Well, other than Eggman doing an oopsie, unless his plan WAS to end the war by drowning the entire planet... What's important is I'm not letting anything happen to my family again!


End file.
